Temperature-Compensated Dispensing of Compressed Gases

ABSTRACT

Method for dispensing a gas comprising (a) providing a gas storage system containing pressurized gas and having at least first and second gas storage volumes, first and second flow control valves in flow communication with the first and second gas storage volumes, respectively, wherein each flow control valve is initially closed, and wherein the first gas storage volume has a smaller volumetric capacity than the second gas storage volume; (b) selecting a reference temperature; (c) measuring the ambient temperature; (d) providing a gas receiving vessel and placing it in flow communication with each flow control valve and with the gas storage system; and (e) initiating delivery of the gas by (i) opening the first flow control valve when the ambient temperature is equal to or greater than the reference temperature or (ii) opening the second flow control valve when the ambient temperature is less than the reference temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application and claims the benefit ofpriority under 35 USC 120 of U.S. patent application Ser. No.12/469,912, filed May 21, 2009, which is a continuation-in-part ofapplication Ser. No. 11/247,566 filed on Oct. 10, 2005. The disclosureof the prior applications are considered part of and are incorporated byreference in the disclosure of this application.

BACKGROUND

The dispensing of compressed gas from a high-pressure storage system toa lower-pressure receiving vessel or tank is known in the art forvarious applications such as supplying fuel to compressed natural gas(CNG)-powered or hydrogen-powered vehicles. When compressed gas istransferred from a high-pressure storage vessel to a lower-pressurevessel, the temperature of the gas in the system changes as a functionof the thermodynamic properties of the gas and the heat transfercharacteristics of the system. Dispensing systems may be designed tocontrol these temperature changes to ensure that the gas transferprocess is timely and efficient.

Cascade filling processes that employ multiple high-pressure storagevessels to charge a lower pressure-receiving vessel are known in theprior art, as exemplified in Borck U.S. Pat. No. 6,779,568. The '568patent discloses that, for a constant filling time, the peak temperatureof the gas in the receiving tank will be lower when a lower pressurestorage vessel is used first during the cascade filling process. Thus,the '568 patent teaches controlling the order in which the storagevessels are utilized based on the difference in pressure within thosestorage banks.

The prior art also teaches that the temperature rise in a receiving tankcan be limited by adjusting the filling rate from the high-pressurestorage vessels, especially at the start of the filling process when therate of temperature increases the greatest, as exemplified in Hwang, etal. U.S. Pat. No. 5,901,758 and Togasawa, et al. U.S. Pat. No.6,598,624.

A further prior art approach for limiting or controlling the temperaturerise in a receiving tank is to utilize additional hardware, such as aheat exchanger to cool the flowing gas stream from the high-pressurestorage vessels, upstream of the receiving tank. The use of suchadditional hardware is disclosed in Sugano, et al. U.S. Pat. No.6,360,793 and Cohen, et al. U.S. Pat. No. 6,619,336.

High-pressure gas storage and dispensing systems are usually installedoutdoors and are subjected to wide ranges of ambient temperatures.Although the above prior art disclosures focus on the thermal impactthat the filling process has on the receiving tank, none of thosedisclosures takes into account, or even recognizes the need to take intoaccount, the impact of ambient temperature on the compressed gas withinand leaving the compressed gas storage system during the process offilling a receiving tank. Based on the limitations of these prior artapproaches for storing and transferring compressed gas fromhigh-pressure storage systems to a lower-pressure receiving vessel,there is a need in the art for improved methods and systems forcontrolling the amount of cooling of the compressed gas within thestorage system during transfer from the storage system to a receivingvessel based on ambient temperature conditions. This need is addressedby the embodiments of the invention described below and defined by theclaims that follow.

BRIEF SUMMARY

The present invention relates to systems and methods for dispensing gasfrom a gas storage system to a gas receiving vessel. There are severalaspects of the invention as outlined below.

Aspect 1. A method for dispensing gas from a gas storage system to a gasreceiving vessel, wherein the method comprises

-   -   (a) providing the gas storage system comprising at least a first        gas storage volume, a first flow control valve in flow        communication with the first gas storage volume, a second gas        storage volume, and a second flow control valve in flow        communication the second gas storage volume, wherein each gas        storage volume contains pressurized gas, wherein each flow        control valve is initially closed, and wherein the first gas        storage volume has a smaller volumetric capacity than the second        gas storage volume;    -   (b) selecting a reference temperature;    -   (c) measuring the ambient temperature adjacent the gas storage        system;    -   (d) providing the gas receiving vessel and connecting the gas        receiving vessel to the gas storage system such that the gas        receiving vessel is in flow communication with each flow control        valve; and    -   (e) initiating delivery of the gas from the gas storage system        to the gas receiving vessel by    -   (i) opening the first flow control valve when the ambient        temperature is equal to or greater than the reference        temperature or    -   (ii) opening the second flow control valve when the ambient        temperature is less than the reference temperature.

Aspect 2. The method of Aspect 1 wherein the flow control valves arefully opened in (e).

Aspect 3. The method of Aspect 1 wherein the gas comprises methane orhydrogen.

Aspect 4. The method of Aspect 1 wherein the reference temperature is inthe range of 0° F. to 50° F., inclusive.

Aspect 5. The method of Aspect 1 wherein the first gas storage systemcomprises a single gas storage vessel in flow communication with thefirst flow control valve and the second gas storage volume comprises aplurality of gas storage vessels in flow communication with the secondflow control valve.

Aspect 6. The method of Aspect 1 which comprises selecting a secondaryreference temperature that is less than the reference temperature of (b)and (iii) when the ambient temperature is equal to or less than lessthan the secondary reference temperature, partially opening the secondflow control valve.

Aspect 7. The method of Aspect 6 wherein the secondary referencetemperature is in the range of 0° F. to −40° F., inclusive.

Aspect 8. A method for dispensing gas from a gas storage system to a gasreceiving vessel, wherein the method comprises

-   -   (a) providing the gas storage system comprising a plurality of        gas storage volumes, a plurality of flow control valves wherein        each gas storage volume has a flow control valve in flow        communication therewith, wherein each gas storage volume        contains pressurized gas, wherein each flow control valve is        initially closed, and wherein the volumetric capacities of the        plurality of gas storage volumes are essentially equal;    -   (b) selecting a reference temperature;    -   (c) measuring the ambient temperature adjacent the gas storage        system;    -   (d) providing the gas receiving vessel and connecting the gas        receiving vessel to the gas storage system such that the gas        receiving vessel is in flow communication with each of the        plurality of flow control valves; and    -   (e) initiating delivery of the gas from the gas storage system        to the gas receiving vessel by        -   (i) opening a first number of the plurality of flow control            valves when the ambient temperature is equal to or greater            than the reference temperature or        -   (ii) opening a second number of gas flow control valves when            the ambient temperature is less than the reference            temperature;

wherein the second number is greater than the first number.

Aspect 9. The method of Aspect 8 wherein second number is two or moreand the first number is one.

Aspect 10. The method of Aspect 8 wherein when the ambient temperatureis equal to or greater than the reference temperature, operating two ormore of the flow control valves by opening and closing each valvesequentially.

Aspect 11. The method of Aspect 8 wherein any of the flow control valvesare fully opened in (e).

Aspect 12. The method of Aspect 8 wherein the gas comprises methane orhydrogen.

Aspect 13. The method of Aspect 8 wherein the reference temperature isin the range of 0° F. to 50° F., inclusive.

Aspect 14. The method of Aspect 8 which comprises selecting a secondaryreference temperature that is less than the reference temperature of (b)and (iii) when the ambient temperature is equal to or less than lessthan the secondary reference temperature, partially opening at least oneof the second number of gas flow control valves.

Aspect 15. The method of Aspect 8 which comprises selecting a secondaryreference temperature that is less than the reference temperature of (b)and (iii) when the ambient temperature is equal to or less than lessthan the secondary reference temperature, opening a third number of gasflow control valves, wherein the third number is greater than the secondnumber.

Aspect 16. The method of Aspect 15 wherein the secondary referencetemperature is in the range of 0° F. to −40° F., inclusive.

Aspect 17. A system for dispensing gas from a gas storage system to agas receiving vessel comprising

-   -   (a) a gas storage system comprising at least a first gas storage        volume, a first flow control valve in flow communication with        the first gas storage volume, a second gas storage volume, and a        second flow control valve in flow communication the second gas        storage volume, wherein each gas storage volume is adapted to        contain pressurized gas, wherein each flow control valve is        adapted to operate in the closed, fully open, and partially open        positions, and wherein the first gas storage volume has a        smaller volumetric capacity than the second gas storage volume;    -   (b) a temperature measuring sensor adapted to measuring the        ambient temperature adjacent the gas storage system;    -   (d) a gas receiving vessel adapted for connection to the gas        storage system such that the gas receiving vessel is in flow        communication with each flow control valve; and    -   (e) a programmable logic controller configured to receive a        temperature-proportional signal from the ambient temperature        measuring sensor, to compare the ambient temperature with a        stored reference temperature, and to operate the flow control        valves such that        -   (i) when the ambient temperature is equal to or greater than            the reference temperature, the first flow control valve is            opened and        -   (ii) when the ambient temperature is less than the reference            temperature, the second flow control valve is opened.

Aspect 18. The system of Aspect 17 wherein the programmable logiccontroller is configured to fully open any of the flow control valves in(e).

Aspect 19. The system of Aspect 17 wherein the programmable logiccontroller is configured to store a secondary reference temperature, tocompare the ambient temperature with the stored reference temperature,and to operate the flow control valves such that (iii) when the ambienttemperature is equal to or less than less than the secondary referencetemperature, partially opening the second flow control valve.

Aspect 20. A system for dispensing gas from a gas storage system to agas receiving vessel comprising

-   -   (a) a gas storage system comprising a plurality of gas storage        volumes, a plurality of flow control valves wherein each gas        storage volume has a flow control valve in flow communication        therewith, wherein each gas storage volume is adapted to contain        pressurized gas, wherein the volumetric capacities of the        plurality of gas storage volumes are essentially equal, and        wherein each flow control valve is adapted to operate in the        closed, fully open, and partially open positions;    -   (b) a temperature measuring sensor adapted to measuring the        ambient temperature adjacent the gas storage system;    -   (d) a gas receiving vessel adapted for connection to the gas        storage system such that the gas receiving vessel is in flow        communication with each flow control valve; and    -   (e) a programmable logic controller configured to receive a        temperature-proportional signal from the ambient temperature        measuring sensor, to compare the ambient temperature with a        stored reference temperature, and to operate the flow control        valves by        -   (i) opening a first number of the plurality of flow control            valves when the ambient temperature is equal to or greater            than the reference temperature or        -   (ii) opening a second number of gas flow control valves when            the ambient temperature is less than the reference            temperature;

wherein the second number is greater than the first number.

Aspect 21. The system of Aspect 20 wherein the programmable logiccontroller is configured to fully open any of the flow control valves in(e).

Aspect 22. The method of Aspect 20 wherein the programmable logiccontroller is configured to, operating two or more of the flow controlvalves by opening and closing each valve sequentially when the ambienttemperature is equal to or greater than the reference temperature.

Aspect 23. The system of Aspect 20 wherein the programmable logiccontroller is configured to store a secondary reference temperature, tocompare the ambient temperature with the stored reference temperature,and to operate the flow control valves such that (iii) when the ambienttemperature is equal to or less than less than the secondary referencetemperature, partially opening at least one of the second number of gasflow control valves.

Aspect 24. The system of Aspect 20 wherein the programmable logiccontroller is configured to store a secondary reference temperature, tocompare the ambient temperature with the stored reference temperature,and to operate the flow control valves such that (iii) when the ambienttemperature is equal to or less than less than the secondary referencetemperature, opening a third number of gas flow control valves, whereinthe third number is greater than the second number.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The invention will be described by way of example with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic view showing a system for controlling thetemperature of compressed gas being transferred from one or morehigh-pressure storage vessels to a receiving vessel in accordance withone embodiment of this invention; and

FIG. 2 is a schematic view of a system for controlling the temperatureof compressed gas being transferred from one or more of high-pressurestorage vessels to a receiving vessel in accordance with a secondembodiment of this invention.

DETAILED DESCRIPTION

The embodiments of this invention relate to methods and systems fordispensing gas from a high-pressure fluid or gas storage system to areceiving vessel by controlling the temperature of the gas in thestorage system during gas transfer to a receiving vessel. By using theseembodiments, the temperature of the components in the storage system,i.e., vessels, piping, valves, and other hardware, can be maintained attemperatures above an allowable minimum temperature below which thesystem components may be subject to mechanical failure. The minimum safeoperating temperature for components in a high-pressure gas storagesystem generally depend upon the materials of construction and designfeatures of the system. A minimum safe operating temperature may be, forexample, −40° F. (−40° C.). At low ambient temperatures, the impact ofisentropic expansion cooling due to the reduction in pressure within thestorage system can be significant, and the temperature within thestorage and delivery system can approach this minimum safe operatingtemperature.

Compressed natural gas (CNG) and hydrogen are the typical componentsdispensed from these storage systems, which are usually installedoutdoors and are therefore subjected to wide ranges of ambienttemperatures. Ambient temperatures are well above the criticaltemperature of hydrogen (−240° C. or −400° F.) and methane (−83° C. or−117° F.), so that these components typically are stored and dispensedas supercritical fluids rather than gases according to strictthermodynamic definitions. However, the terms “gas” and “compressed gas”are usually used in the art as generic terms for both gases andsupercritical fluids. In the present disclosure, the terms “gas” and“compressed gas” may be used interchangeably and are meant to includeelements and compounds in both thermodynamic states of gas andsupercritical fluid. The generic term “fluid” as used herein includesboth thermodynamic states of gas and supercritical fluid.

A gas dispensing system is defined as a pressurized gas storage andsupply system for providing pressurized gas to a portable receiving tankor vessel. The gas dispensing system includes a connector to couple withthe receiving vessel for gas transfer and an appropriate safetyinterlock system to ensure safe operation during the filling step. Thereceiving tank or vessel typically is part of a vehicle such as a car,truck or bus.

The indefinite articles “a” and “an” as used herein mean one or morewhen applied to any feature in embodiments of the present inventiondescribed in the specification and claims. The use of “a” and “an” doesnot limit the meaning to a single feature unless such a limit isspecifically stated. The definite article “the” preceding singular orplural nouns or noun phrases denotes a particular specified feature orparticular specified features and may have a singular or pluralconnotation depending upon the context in which it is used. Theadjective “any” means one, some, or all indiscriminately of whateverquantity.

In the present disclosure, the term “in flow communication with” asapplied to a first and second region or volume means that a fluid canflow from the first region or volume to the second region or volumethrough connecting piping and/or an intermediate region or volume. Theterms “connecting” and “connected to” as applied to a first and secondregion or volume means that a fluid can flow from the first region orvolume to the second region or volume through connecting piping. Theterm “in flow communication with” applies to systems in which a valve isinstalled between the first and second region or volume such that (1)gas flow actually occurs, i.e., when the valve is open, or (2) gas flowcan potentially occur, i.e., when the valve is closed and has thepotential for being opened.

The adjective “open” when applied to a flow control valve means anyposition of the valve flow control member, e.g., a valve stem,diaphragm, butterfly, rotating ball, and the like, that allows gas toflow through the valve. The adjective “open” thus may apply to apartially-open or fully-open flow control valve. The verbs “open” and“opening” mean the act of moving the valve flow control member from aclosed position to a partially open position or to a fully openposition. The term “closed” has the usual meaning of a valve in which nogas flow occurs because the flow control member is in the closedposition.

The term “volumetric capacity” when applied to a gas storage vessel or agas storage volume means the volume within the gas storage vessel or agas storage volume. A gas storage volume is defined as a single gasstorage vessel or a plurality of gas storage vessels wherein each vesselis in flow communication with the other vessels.

The embodiments of the invention relate to the phenomenon wherein gasflowing from a high-pressure storage volume (which may comprise one ormore vessels) to a lower-pressure receiving vessel is cooled byisentropic pressure decrease in the storage volume. As a result, the gasleaving the storage volume and the storage volume itself are below theinitial ambient temperature of the storage volume. The temperaturedecrease and the degree of cooling of the gas are related to thepressure decrease in the storage volume according to known thermodynamicprinciples. The pressure decrease in the storage volume is proportionalto the volumetric ratio of the receiving vessel to the storage volume,and the pressure decrease in the storage volume increases as thisvolumetric ratio increases. Thus the temperature drop in the storagevolume increases as the volumetric ratio of the receiving vessel to thestorage volume increases. For a receiving vessel with a given volume,therefore, decreasing the size of the storage volume will result in agreater temperature drop in the gas storage volume.

In gas dispensing systems, cooling of the gas being transferred to thereceiving tank may be desirable. The cooling of the gas in the gasstorage vessel or vessels due to isentropically decreasing pressure isacceptable as long as the temperature of the storage system components(i.e., vessels, piping, valves, and other hardware) is above the minimumsafe operating temperature. At higher ambient temperatures, more coolingof the gas in the storage volume is possible before the minimum safeoperating temperature is approached, and the minimum safe operatingtemperature may never be reached during gas transfer at higher ambienttemperatures. At lower ambient temperatures, however, the possibility ofreaching the minimum safe operating temperature increases, andoperational steps may be required in certain situations to avoidreaching the minimum safe operating temperature of the gas storagesystem. The embodiments of the present invention address thisrequirement.

The allowable pressure decrease in a storage volume is determined by twoparameters, namely, the ambient temperature surrounding the gas storagesystem and the minimum safe operating temperature. As discussed above,the minimum safe operating temperature for components in a high-pressuregas storage system typically depends on materials of construction anddesign features, and this temperature may be unique to each to gasstorage system design. A typical minimum safe operating temperature is,for example, −40° F. (−40° C.).

An exemplary embodiment of the invention is illustrated in FIG. 1, whichis a schematic flow diagram of a storage and delivery system forcompressed gas in accordance with this embodiment. Storage and deliveryor gas dispensing system 10 includes a storage section 12 and aplurality of compressed gas storage vessels 14, 16, 18, 20, 22, and 24.The number of storage vessels in the storage and delivery system may bevaried; the exact number of vessels is not a limitation on theembodiments of this invention. The storage vessels may be filled to highpressures up to, for example, 480 barg (7000 psig).

As can be seen in FIG. 1, the six storage vessels are arranged in threestorage banks 26, 28, and 30 and have different total volumes. Thestorage bank 26 includes three storage vessels 14, 16, and 18; thesecond storage bank 28 includes two storage vessels 20 and 22 and thethird storage bank 30 includes the single storage vessel 24. Thus, eachof the storage banks 26, 28, and 30 has a different compressed gasstorage volume or volumetric capacity.

Still referring to FIG. 1, each bank of storage vessels is in flowcommunication with a separate flow control device. The flow controldevices may be gas flow control valves 32, 34, and 36, respectively,each of which typically are operable either in a fully-opened orfully-closed position. Any of the valves may be operable inpartially-open positions to reduce gas flow rates if desired. As can beseen in FIG. 1, the flow control valve 32 controls the flow ofcompressed gas from the three storage vessels 14, 16, and 18 in bank 26as a unit and directs that flow into a supply line 38 for delivery to areceiving tank 40. In a similar manner, the flow control valve 34controls the flow of compressed gas from the storage vessels 20 and 22,which constitute the second bank 28 of storage vessels. When this secondvalve 34 is opened, it places the second bank of storage vessels in flowcommunication with the supply line 38 for delivery of compressed gas tothe receiving tank 40. Control valve 36 controls the flow of compressedgas from the single storage vessel 24, which constitutes the third bank30. When the valve 36 is opened, it directs the flow of compressed gasthrough supply line 38 to the receiving tank.

When each of the banks 28, 30, and 32 of storage vessels is placed inflow communication with receiving vessel 40, the pressure in the storagevessels communicating with the receiving vessel decreases as gas flowsfrom the storage vessels into the receiving vessel until the pressure inthe storage vessels communicating with the receiving vessel equalizewith the internal pressure of the receiving vessel. At that point intime the gas flow from the bank(s) of storage vessels communicating withthe receiving vessel ends. Alternatively, gas flow may be terminatedbefore full equalization by closing the appropriate valves.

As can be seen in FIG. 1, the group of two storage vessels 20, 22constituting the second bank 28 has twice the total gas storage volumeor volumetric capacity as the single storage vessel 24 constituting thethird bank 30, and the three storage vessels 14, 16 and 18 constitutingthe first bank 28 has three times the total storage volume as the singlestorage vessel 24 constituting the third bank 30. Thus the gas storagevolume that communicates with the receiving vessel 40 through the supplyline 38 can be varied by selectively opening one or more of the flowcontrol valves 32, 34, and 36.

Still referring to FIG. 1, a temperature measuring device or sensor 42is provided to measure the ambient temperature adjacent the gas storageand delivery system 10 and is adapted for communicatingtemperature-proportional signals to programmable logic controller 44.The programmable logic controller 44 operates the flow control valves32, 34, and/or 36 in a programmed sequence based upon the ambienttemperature measured by the temperature measuring device 42. Inembodiments of this invention, the programmable logic controller 44includes a reference temperature that is compared to the measuredambient temperature, and the relationship between these two temperaturesis utilized by the programmable logic controller 44 to control theopening or sequencing of the one or more of the flow control valves 32,34, and 36. Alternatively, programmable logic controller 44 may operatethe flow control valves 32, 34, and 36 so that one or more of the valvesare in the partially-opened position to control the gas flow rate orflow rates at less than the maximum flow rate or rates when the valvesare fully open.

The reference temperature may be selected or preset by the designerand/or operator of the gas storage and delivery system 10 based on thespecific system design characteristics and/or operating experience withthe system. These typically include, for example, the heat transfercharacteristics of the storage vessel and piping system, vessel size,and other features that can affect gas flow rate and pressure drop. Thereference temperature typically is in the range of 0° F. to 50° F.,inclusive, although a reference temperature outside this range may beused if desired.

Programmable logic controller 44 can be programmed to vary the number ofvalves that are opened at any given time, as well as the order in whichthose valves are opened, depending upon the desired or allowable amountof cooling of the compressed gas being transferred to the receiving tank40. In one embodiment, the storage and delivery system 10 is designed todeliver the coldest gas possible to the receiving vessel 40 when theambient temperature measured by the device 42 is higher than thereference temperature in the programmable logic controller 44, and thecooling of the compressed gas transferred to the receiving tank 40 isdesirably minimized when the ambient temperature measured by the device42 is less than the reference temperature in the programmable logiccontroller 44.

In particular, the greater the pressure decrease that occurs in thesupply vessel, the greater the cooling effect that occurs in the supplyvessel. The greatest pressure decrease is achieved by deliveringcompressed gas to the receiving vessel 40 from the smallest availablevolume storage vessel (i.e., 24) in the storage section 12 of thesystem.

A second embodiment of a storage and delivery system is illustrated inFIG. 2. The storage and delivery system 100 includes a storage section102 having a plurality of storage vessels or cylinders 104, 106, 108,110, 112, and 114. Although the storage section 102 is illustrated asincluding six separate storage vessels, the number of vessels can bevaried in accordance with other embodiments of this invention.

Still referring to FIG. 2, each of the storage vessels is in flowcommunication with a separate gas flow control valve 104A, 106A, 108A,110A, 112A, and 114A, respectively. Any of these valves can be operatedas on-off valves or alternatively can be operated in thepartially-opened position to control the gas flow rate or flow rates atless than the maximum flow rate or rates when the valves are fully open.

Each of the flow control valves flow control is in flow communicationwith a common feed line or manifold 116, which is in flow communicationwith a supply line 118 for directing the flow of compressed gas from oneor more of the storage vessels 104, 106, 108, 110, 112, and 114 to areceiving tank or vessel 120.

Still referring to FIG. 2, a temperature measuring device 122 measuresthe ambient temperature in the same manner as the temperature measuringdevice 42 employed in the storage and delivery system 10. Also, thestorage and delivery system 100 includes a programmable logic controller124 including a reference temperature stored therein. This programmablelogic controller 124 may be of the same type as the programmable logiccontroller 44 of storage and delivery system 10, but the controller isprogrammed to operate the valves 104A, 106A, 108A, 110A, 112A, and 114Aas described below.

In accordance with the operation of the storage and delivery system 100,the ambient temperature measured by the temperature measuring device 122is compared to the reference temperature in the programmable logiccontroller, and based upon that comparison, the programmable logiccontroller operates the various control valves 104A, 106A, 108A, 110A,112A, and 114A in a programmed manner to aid in controlling thetemperature of compressed gas being transferred from one or more of thehigh-pressure storage vessels, 104, 106, 108, 110, 112, and 114 to thereceiving tank or vessel 120. As discussed above, the referencetemperature may be selected or preset by the designer and/or operator ofthe gas storage and delivery system 10 based on the specific systemdesign characteristics and/or operating experience with the system.These may include, for example, the heat transfer characteristics of thestorage vessel and piping system as well as other characteristics thatmay affect gas flow rate and pressure drop.

For example, when the ambient temperature measured by the device 122 isgreater than a reference temperature in the programmed logic controller124 of 10° F.), the compressed gas being transferred to the receivingtank or vessel 120 may be cooled to the maximum extent, and theprogrammable logic controller in this case would be programmed toselectively open and close each of the valves 104A, 106A, 108A, 110A,112A, and 114A, one valve at a time, i.e., sequentially. In this manner,at any specific time in the gas transfer operation only one of thestorage tanks 104, 106, 108, 110, 112, and 114 will be directing theflow of compressed gas into the receiving tank or vessel 120. Thevolumetric capacities of the storage vessels 104, 106, 108, 110, 112,and 114 may be essentially equal, which means that the differencebetween the volumes of any two vessels is less than 5% of the average ofthe volumes of the two vessels.

In this mode of operation, the order in which the individual flowcontrol valves are opened is not important, but it is desirable thatonly one valve at a time be opened and closed, i.e., that the valves beoperated sequentially. This provides for the greatest degree of pressuredecrease in the storage vessels until full or partial pressureequalization takes place with the receiving vessel 120, therebydelivering the coldest gas possible by taking maximum advantage of thecooling resulting from the gas pressure decrease in each storage vessel.

The programmable logic controller 124 can be programmed to override theabove operating sequence (or any other sequence being carried out) asdesired. However, when the ambient temperature is less than thereference temperature (for example, less than a reference temperature of10° F.), this generally indicates that the compressed gas beingtransferred from the storage section 102 to the receiving tank or vessel120 does not require significant cooling. Accordingly, the programmablelogic controller 124 can be programmed to open more than one controlvalve at a time. For example, control valves 104A and 106A can be openedfirst when the temperature is less than the reference temperature of 10°F. but more than a second reference temperature of 1° F. Another valve(for example, control valve 108A) could be opened if the temperaturefalls below 1° F. Ultimately, all of the valves can be opened at thesame time at a third reference temperature of −30° F. to minimize thedegree of cooling in the gas storage system.

The operation of the storage and delivery systems 10 and 100 describedabove, including the sequence of valve operation, may be varied withinwide limits. A common feature of the embodiments of this invention isthat the systems are designed to control the temperature of thecompressed gas being transferred from one or more high-pressure storagevessels to a receiving vessel based upon ambient temperature conditionsin order to protect the storage system against possible damage attemperatures at or below the minimum safe operating temperature.

Other embodiments of the invention are possible. For example, thestorage and delivery system 10, rather than employing three separategroups of storage vessels in which each storage vessel has essentiallythe same volume, can be designed so that each of the groups 26, 28, and30 is replaced by a single storage vessel, with the storage volume ofeach vessel differing from the storage volume in every other vessel. Forexample, the bank 26 of vessels 14, 16, and 18 could be replaced by asingle storage vessel having a storage volume corresponding to the totalstorage volume provided by the storage vessels 14, 16, and 18. Likewise,the storage vessels 20 and 22, constituting the second bank 28 ofstorage vessels can be replaced by a single storage vessel having astorage volume equivalent to the total storage volume of the vessels 20and 22. In this embodiment the storage vessel 24 will remain, presentingthe desired storage vessel volume to be controlled by the supply valve36.

In the illustrative embodiments described above, the flow control valvesare operated in either fully-open or fully-closed positions. Otherembodiments are possible in which a flow control valve is operated inthe partially-open position to reduce the gas flow rate under certainselected conditions. In an alternative embodiment, for example, the flowrate of gas being transferred at a very low ambient temperature may bereduced by partially closing the flow control valve so that the rate ofpressure decrease and the degree of cooling in the storage vessel arereduced. This alternative embodiment utilizes the system of FIG. 1 inwhich the gas storage banks 26, 28, and 30 are in flow communicationwith the flow control valves 32, 34, and 36, respectively, and thesevalves are in flow communication with receiving tank 40. A primaryreference temperature is selected or preset and stored in theprogrammable logic controller 44 similar to the embodiments describedabove. The primary reference temperature may be in the range of 0° F. to50° F., inclusive. In addition, a secondary reference temperature isselected or preset and stored in the programmable logic controller 44wherein the secondary reference temperature is less than the primaryreference temperature. The secondary reference temperature may be in therange of 0° F. to −40° F., inclusive.

The system of FIG. 1 is operated in this alternative embodiment asfollows. If the ambient temperature measured by the temperature sensor42 is at or above the primary reference temperature, the flow controlvalve 36 is fully opened by the programmable logic controller 44, andgas flows from the storage vessel 24 to the receiving tank 40. In thiscase, maximum cooling occurs due to the rapid pressure decrease in thestorage tank 24. The gas flow continues until the pressure in thereceiving tank 40 reaches a desired pressure. If there is insufficientgas in the storage vessel 24 to provide the desired pressure in thereceiving tank, the programmable logic controller 44 closes valve 36 andfully opens the flow control valve 34. Additional gas flows into thereceiving tank 40, but the degree of cooling is less than in theprevious step. When the pressure in the receiving tank reaches thedesired pressure, the programmable logic controller 44 closes valve 34.

If the ambient temperature measured by the temperature sensor 42 isbelow the primary reference temperature and at or above the secondaryreference temperature, the flow control valve 32 is fully opened by theprogrammable logic controller 44, and gas flows from the storage bank 26to the receiving tank 40. In this case, a reduced degree of coolingoccurs due to the slower pressure decrease in the storage tanks 14, 16,and 18 when compared with the gas flow from the storage vessel 24described above. The gas flow continues until the pressure in thereceiving tank 40 reaches a desired pressure, and the programmable logiccontroller 44 closes valve 32.

If the ambient temperature measured by the temperature sensor 42 isbelow the secondary reference temperature, the flow control valve 32 ispartially opened by the programmable logic controller 44, and gas flowsat a reduced rate from the storage bank 26 to the receiving tank 40 ascompared with the flow when valve 32 is fully open as described above.In this case, a further reduced degree of cooling occurs due to theslower pressure decrease in the storage tanks 14, 16, and 18. The gasflow continues until the pressure in the receiving tank 40 reaches adesired pressure, and the programmable logic controller 44 closes valve32. This operating mode is selected at very low ambient temperatures toensure that the temperature in the storage bank 26 is above the minimumsafe operating temperature.

In the exemplary embodiment described above, for example, the primaryreference temperature may be 20° F. and the secondary referencetemperature may be −20° F. Other primary and secondary referencetemperatures may be selected as required based on equipment designfeatures and operating parameters.

In another embodiment, the ambient temperature measured by the device 42may be greater than the reference temperature in the programmable logiccontroller (e.g., 10° F.), thereby establishing that the cooling of thegas should be maximized as it is being transferred to the receivingvessel 40. The programmable controller 44 will first open valve 36 toestablish flow communication only between the storage volume of storagevessel 24 and the receiving vessel 40. The pressure in the storagevessel 24, because this vessel has the smallest storage volume fordelivering compressed gas to the receiving vessel 40, decreases to thegreatest degree possible in equalizing with the pressure in thereceiving vessel, thereby delivering the coldest gas possible by takingmaximum advantage of expansion cooling. Next, the programmable logiccontroller 44 will open the valve 34 to communicate storage vessels 20,22 of bank 28 with the receiving vessel 40, and thereafter will opencontrol valve 32 for communicating the three storage vessels 14, 16 and18 of bank 26 with the receiving vessel 40, thereby delivering a lowerproportion of the compressed gas to the storage vessel 40 at warmertemperatures.

Alternatively, when the ambient temperature is less than the set pointof the programmable logic controller, cooling of the gas during thetransfer operation is not desirable. Under these conditions, theprogrammable logic controller 44 is programmed to open valve 32 first toplace supply vessels 14, 16, and 18 of bank 26 in flow communicationwith the receiving tank 40. The pressure in vessels 14, 16, and 18 doesnot decrease as much as the pressure would have decreased in storagevessel 24 on a warmer day when the ambient temperature was greater thanthe reference temperature of the programmable logic controller. Thecooling of the compressed gas due to pressure decrease in supply vessels14, 16, and 18 is therefore minimized.

The storage and delivery methods and systems described above can beused, for example, for the refueling of vehicles powered by compressednatural gas (CNG) or hydrogen in locations where low ambienttemperatures could result in damage to gas storage systems by very lowtemperatures caused by cooling due to pressure decrease in gas storagevessels during operation. The embodiments described above may be useful,for example, at locations having minimum ambient temperatures belowabout 20° F.

1. A method for dispensing gas from a gas storage system to a gasreceiving vessel, wherein the method comprises (a) providing the gasstorage system comprising at least a first gas storage volume, a firstflow control valve in flow communication with the first gas storagevolume, a second gas storage volume, and a second flow control valve inflow communication the second gas storage volume, wherein each gasstorage volume contains pressurized gas, wherein each flow control valveis initially closed, and wherein the first gas storage volume has asmaller volumetric capacity than the second gas storage volume; (b)selecting a reference temperature; (c) measuring the ambient temperatureadjacent the gas storage system; (d) providing the gas receiving vesseland connecting the gas receiving vessel to the gas storage system suchthat the gas receiving vessel is in flow communication with each flowcontrol valve; and (e) initiating delivery of the gas from the gasstorage system to the gas receiving vessel by (i) opening the first flowcontrol valve when the ambient temperature is equal to or greater thanthe reference temperature or (ii) opening the second flow control valvewhen the ambient temperature is less than the reference temperature. 2.The method of claim 1 wherein the flow control valves are fully openedin (e).
 3. The method of claim 1 wherein the gas comprises methane orhydrogen.
 4. The method of claim 1 wherein the reference temperature isin the range of 0° F. to 50° F., inclusive.
 5. The method of claim 1wherein the first gas storage system comprises a single gas storagevessel in flow communication with the first flow control valve and thesecond gas storage volume comprises a plurality of gas storage vesselsin flow communication with the second flow control valve.
 6. The methodof claim 1 which comprises selecting a secondary reference temperaturethat is less than the reference temperature of (b) and (iii) when theambient temperature is equal to or less than less than the secondaryreference temperature, partially opening the second flow control valve.7. The method of claim 6 wherein the secondary reference temperature isin the range of 0° F. to −40° F., inclusive.
 8. A system for dispensinggas from a gas storage system to a gas receiving vessel comprising (a) agas storage system comprising at least a first gas storage volume, afirst flow control valve in flow communication with the first gasstorage volume, a second gas storage volume, and a second flow controlvalve in flow communication the second gas storage volume, wherein eachgas storage volume is adapted to contain pressurized gas, wherein eachflow control valve is adapted to operate in the closed, fully open, andpartially open positions, and wherein the first gas storage volume has asmaller volumetric capacity than the second gas storage volume; (b) atemperature measuring sensor adapted to measuring the ambienttemperature adjacent the gas storage system; (d) a gas receiving vesseladapted for connection to the gas storage system such that the gasreceiving vessel is in flow communication with each flow control valve;and (e) a programmable logic controller configured to receive atemperature-proportional signal from the ambient temperature measuringsensor, to compare the ambient temperature with a stored referencetemperature, and to operate the flow control valves such that (i) whenthe ambient temperature is equal to or greater than the referencetemperature, the first flow control valve is opened and (ii) when theambient temperature is less than the reference temperature, the secondflow control valve is opened.
 9. The system of claim 8 wherein theprogrammable logic controller is configured to fully open any of theflow control valves in (e).
 10. The system of claim 8 wherein theprogrammable logic controller is configured to store a secondaryreference temperature, to compare the ambient temperature with thestored reference temperature, and to operate the flow control valvessuch that (iii) when the ambient temperature is equal to or less thanless than the secondary reference temperature, partially opening thesecond flow control valve.